1. Field of the Invention
The invention relates to a method for calibrating a projector, more particularly to a method and system for automatic color wheel calibration in a projector.
2. Description of the Related Art
Digital light processing (DLP) projectors using a single digital micro-mirror device (DMD) chip are the more commonly used types of projectors currently available on the market. Such DLP projectors require use of a color wheel to separate colors, and the colors required by each pixel are reflected to a display screen using the DMD chip. However, since the color wheel of the conventional projector that uses a single DMD chip can only process one color at a time, loss of some of the luminance may result. In addition, since the spectral wavelength characteristics of different colored lights may vary, the colors cannot be truly recovered. Particularly, the color red is oftentimes not sufficiently sharp or vivid enough when expressed in a colored image. Therefore, how to enable a projector to possess sufficient displaying luminance while ensuring true recovery of colors is a key issue that projector manufacturers are faced with in designing products, and color wheel design is the most important factor.
Referring to FIG. 1, a conventional six-segment color wheel is designed to have three non-primary colors, e.g., white (W), yellow (Y) and cyan (C), in addition to the three primary colors of red (R), green (G), and blue (B). To make the best use of the color wheel and to enhance the utilization efficiency of the color wheel, a projector will mix the three primary colors having suitable color levels to produce other non-primary colors. In this way, one revolution of the color wheel will produce two non-primary color lights of the same color, so that the projector has sufficient displaying luminance and the colors can be more truly recovered. Therefore, the color level values of the three primary colors to produce the other non-primary colors need to be recorded in the projector.
One conventional way to determine the color level values of the three primary colors is to divide each non-primary color zone of the color wheel into a plurality of sub-color blocks, e.g., dividing the yellow color zone into sub-color blocks Y1, Y2, Y3, and Y4, and projecting the color of one of the sub-color blocks, e.g., Y1, and a combination of the three primary colors that have suitable color level values onto left and right halves of a screen (i.e., side by side), respectively. Subsequently, the color level values of the three primary colors are adjusted through naked eye inspection and with the aid of a color adjusting tool, CIE xy (color calibration software loaded in a computer connected to the projector). The color level values of the three primary colors are adjusted until the color produced on the screen by the combination of the three primary colors having certain color level values matches the color of the sub-color block Y1. The projector is then caused to record the color level values of the three primary colors last adopted by the projector. The above steps are subsequently repeated for the rest of the sub-color blocks Y1, Y2, Y3, and Y4 until corresponding color level values of the three primary colors are obtained for all of the sub-color blocks Y1, Y2, Y3, and Y4. The above steps are further repeated to determine the corresponding color level values of the three primary colors for the sub-color blocks of the other non-primary colors, e.g., sub-color blocks W1, W2, W3, and W4 of the color white, and sub-color blocks C1, C2, C3, and C4 of the color cyan.
However, the use of naked eye inspection to determine the corresponding color level values of the three primary colors for the sub-color blocks of each non-primary color is not only time-consuming but also inaccurate.